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The epididymis (/ ɛ p ɪ ˈ d ɪ d ɪ m ɪ s /; pl.: epididymides / ɛ p ɪ d ɪ ˈ d ɪ m ə d iː z / or / ɛ p ɪ ˈ d ɪ d ə m ɪ d iː z /) is an elongated tubular genital organ attached to the posterior side of each one of the two male reproductive glands, the testicles.
[9] [10] [11] Moreover, this increase in scrotal storage of sperm corresponds with epididymis evolution from reptiles to mammals. The mechanism by which sperm storage in the epididymis is enhanced at lower extra-abdominal temperatures has been shown to be a consequence of the biophysics of oxygen availability and sperm oxidative respiration. [12]
It was once theorized that birds used their air sacs to cool the testes internally, but later studies revealed that birds' testes are able to function at core body temperature. [65] Some mammals with seasonal breeding cycles keep their testes internal until the breeding season. After that, their testes descend and increase in size and become ...
The epididymis is a long whitish mass of tightly coiled tube. The sperm that are produced in the seminiferous tubules flow into the epididymis. During passage via the epididymis, the sperm undergo maturation and are concentrated by the action of ion channels located on the apical membrane of the epididymis. [2]
A large part of the head end of the mesonephros atrophies and disappears; of the remainder the anterior tubules form the efferent ducts of the testicle; while the posterior tubules are represented by the ductuli aberrantes, and by the paradidymis, which is sometimes found in front of the spermatic cord above the head of the epididymis.
If the fetus has testes and the testes produce testosterone, and if the cells of the genitals respond to the testosterone, the outer urogenital folds swell and fuse in the midline to produce the scrotum; the protuberance grows larger and straighter to form the penis; the inner urogenital swellings grow, wrap around the penis, and fuse in the ...
As a result of the epididymis being attached to the testis, and the cauda epididymis extending below the lower extremity of the testis (Figure 1C), it was proposed that the epididymis was the prime mover in the evolution of testicular decent, whereby the cauda epididymis preceded the testis into a scrotal location. [1]
In humans and other large mammals, there are approximately 15 to 20 efferent ducts, which also occupy nearly one-third of the head of the epididymis. b) single entry, as seen in most small animals such as rodents, whereby the 3–6 ductules merge into a single small ductule before entering the epididymis. [citation needed]